Pittsburgh Cob Home Building Update

Cob Home Design

So the wife and I found the land we want to build on inside of the city of Pittsburgh and we’ve got an email into BBI asking what information they will need to give us a building permit and ultimately an occupancy permit. We’ve also got an email into the local community group. As the land is city owned (actually URA owned) we need their approval for our project. I know some people might find that to be a huge pain but I actually really like that – maybe it has something to do with the fact that I am a VP on the board of directors of a similar community group.

Learning to build cob

While we are waiting to hear back from BBI and to have our meeting with the community group we are not sitting on our hands. We’ve been reaching out to others in and around Pittsburgh who may have some interest in what we are doing as well as talking to people around the country who have already built cob houses to find out how they got their buildings to pass inspection or what tested they had to have conducted for a structural engineer or architect to sign off of the building.

Compressive Strength vs. Tensile Strength

One thing we found is that the straw that is required for tensile strength brings down the compressive strength so we’ve looked into different types of pozzolans (additives) and while fly ash is abundant and free in Western PA we are worried about it’s toxicity. The soil we are going to be using will already probably contain some amount of lead so we want to use the cleanest stuff available.

It seems like pumice is probably our best bet. While pumice is not going to be able to be locally sourced it will not only make the cob stronger but will also make it lighter allowing us to build faster. It also adds insulation (or R) value. It will increase our cost for the cob but will lower the cost on the plaster side as we won’t need a full 4 inches of plaster to increase the R value as much.

If you are interested in learning more or in helping us when the project gets underway use the contact form or leave a comment and thank you for your interest!